Vibratory treatment apparatus

ABSTRACT

This invention relates to an ultrasonic vibratory treatment apparatus which is particularly useful in ultrasonically cleaning or etching semiconductor bodies comprising the following elements: an etchant-resistant receptacle having a plurality of retaining walls; at least one vibration-generating transducer; a vibration-transferring epoxy-adhesive layer having a vibrationtransferring portion and an anchoring portion between the receptacle and the transducer; and a heat-transfer element which is imbedded in the adhesive layer. The vibration-transferring portion is directly adhered to both the bottom surface of the transducer and one of the retaining walls. The anchoring portion surrounds the vibration-transferring portion and part of the transducer thereby securing the transducer to one of the walls of the receptacle. The receptacle, the transducer, the epoxyadhesive layer and the heat-transfer element are all correlated to produce a standing-wave system in a liquid having a known cavitation threshold in the receptacle responsive to a particular power input to the transducer.

United States Patent 3,480,258 11/1969 Massa ABSTRACT: This inventionrelates to an ultrasonic vibratory treatment apparatus which isparticularly useful in ultrasonically cleaning or etching semiconductorbodies comprising the following elements: an etchant-resistantreceptacle having a plurality of retaining walls; at least onevibration-generating transducer; a vibration-transferring epoxy-adhesivelayer having a vibration-transferring portion and an anchoring portionbetween the receptacle and the transducer; and a heattransfer elementwhich is imbedded in the adhesive layer. The vibration-transferringportion is directly adhered to both the bottom surface of the transducerand one of the retaining walls. The anchoring portion surrounds thevibration-transferring portion and part of the transducer therebysecuring the transducer to one of the walls of the receptacle. Thereceptacle, the transducer, the epoxy-adhesive layer and theheattransfer element are all correlated to produce a standing-wavesystem in a liquid having a known cavitation threshold in the receptacleresponsive to a particular power input to the transducer.

PATENTEDnmms-n 3527278 FlG.2.

mvamons;

PAUL L. DEE, I 2 RICHARD L.EDWARDS,

Hmong. LEE, BYfiwL k THEI ATTORNE VlllBRATGlRY TREATMENT APPARATUS Thisinvention relates to an ultrasonic vibratory treatment apparatus capableof producing a standing-wave system in a body of liquid containedtherein and is particularly useful in the etching and cleaningoperations used in the manufacturing of semiconductor devices.

in order to produce a standing-wave system (i.e., a continuous,periodically varying sinusoidal wave) in a body of liquid held in areceptacle, a number of factors must be considered including thecavitation threshold of the liquid, the frequency of the ultrasonictransducer, the input power to the transducer and the thickness of thereceptacle directly below the area where the transducer is attached tothe receptacle. When all the above factors are properly correlated, theyproduce a standing-wave system which in turn generates a cavitationcycle. Cavitation is defined as the continuous forming and collapsing ofmillions of tiny bubbles in a body of liquid while under the influenceof a standing-wave system; the magnitude of the cavitation determinesthe speed of the cleaning action.

The ultrasonic transducer converts the predetermined electrical inputreceived from a generator into vibratory mechanical or acoustic energyof sufficient intensity to induce cavitation and cleaning. Generally,the transducer is attached to the bottom of the receptacle to developuniform cavitation fields along the entire bottom surface of thereceptacle. To increase the distance the cavitation is effectivelyproduced from this bottom surface, the power input is increased. Inaddition, the thickness of the bottom wall of the receptacle is matchedwith the frequency of the transducer to minimize any dampening effects,i.e., as the thickness of the bottom wall increases the dampening effectincreases. This is because sound intensity diminishes in accordance withthe universally applicable inverse square law.

To illustrate the effect of the above factors in a practical example letus consider the following situation. Ultrasonic energy propagating atabout 1,400 meters per second through fresh deionized water at afrequency of 20 kilohertz has a wavelength of about 7 centimeters. Ifthe vibratory surface of the 20-kilohertz transducer is attached to thebottom surface of a receptacle, it is possible to establish astanding-wave system in a vertical direction. The periodic energytravels up to the surface of the liquid and is reflected back down againto the bottom of the receptacle. A standing wave thus automaticallyestablishes itself in water if the liquid level is an even multiple ofthe wavelength dimension away from the source, divided by two. Thus atlevels of 3.5, 7, 10.5 centimeters and so on, a standing-wave system isestablished. If the level of the fresh water was lowered to lcentimeter, it would be necessary to retune the generator by asufficient amount-up to 28 kilohertz-to reestablish the standing wave.

The number of transducers needed to establish a standing wave in a givenreceptacle varies depending on desired results. To answer the questionhow many transducers and how much ultrasonic power is required, one mustfirst examine the values of the cavitation threshold for variousliquids. These vary from roughly 0.3 watt per square centimeter oftransducer vibrating area for fresh water at frequencies up to about 10kilohertz, to values 10 times higher for more viscous liquids andsolvents. Above 10 kilohertz increasingly higher sonic thresholdintensity are required. For example, roughly 10 watts per squarecentimeter is required for water at 200 kilohertz. The magnitude foreach application depends on the degree of impurities encountered,desired cleaning time, equipment cost, and the sophistication of theequipment. Therefore, once sufficient sound intensity is generated inthe liquid to overcome the cavitation threshold, cavitation will occur.

In the prior art of etching and cleaning semiconductor materials it hasbeen very difficult to automate this process when metallic ultrasonictanks are used because the etchants and solvents oftentimes attacked themetal tanks containing the etchant or solvent. To date the use of anultrasonic tank made of a suitable chemical and etchant-resistantplastic which would eliminate this problem was thought to be impracticalbecause no one had yet found a way to mount a vibratory transducer tothis type of plastic material. Furthermore, it had been assumed that aplastic material would have a dampening effect on the transducersability to change electrical to mechanical energy thereby making it anunsuitable material for forming ultrasonic tanks.

Accordingly, it is an object of this invention to provide an ultrasonicvibratory treatment apparatus which is particularly useful for agitationof a body of liquid to promote accelerated and enhanced action of theliquid, such as cleaning or etching action, on objects immersed therein.

It is another object of this invention to provide an ultrasonicvibratory treatment apparatus which will minimize any dampening effectsduring the conversion of electrical to mechanical energy while at thesame time providing a standing-wave system.

It is still another object of this invention to provide an ultrasonicvibratory treatment apparatus which is suitable for use in a processsystem consisting of a plurality of units of such apparatus each beingcapable of modifications in structure wherein such modifications areprimarily predetermined by the type of liquid solution contained in eachapparatus and the use to which the solution will be put.

These and other objects of this invention will be apparent from thefollowing description and the accompanying drawing, wherein:

FIG. 1 is a frontal view of a preferred embodiment of this invention.

FIG. 2 is an enlarged cross-sectional view of a portion of the apparatusshown in FIG. ll.

Briefly, this invention relates to an ultrasonic vibratory treatmentapparatus which is capable of ultrasonically cleaning or etchingsemiconductor devices. The apparatus comprises an etchant-resistantreceptacle, at least one vibrationgenerating transducer, avibration-transferring epoxy-adhesive layer attaching the transducer tothe receptacle and a heat-transfer member embedded in the epoxy adhesivelayer. The above elements of the apparatus are all adapted so that incombination, they generate a standing-wave system in a liquid having aknown cavitation threshold in the receptacle responsive to a particularpower input to the transducer.

Referring to FIGS. 1 and 2 there is shown one preferred embodiment ofour ultrasonic vibratory treatment apparatus ll. The apparatus llincludes a chemicaland etchant-resistant receptacle 2 for containing abody of liquid, having a bead 7 around its bottom surface, a pluralityof retaining walls 3 and a top lip 5 having an opening 6 therethrough,one or more vibration-generating transducers 110, a heat-conductiveepoxy layer llll interposed between the receptacle 2 and the transducers10 not visible in FIG. l but shown in H0. 2 and a heat-transfer element4 embedded in the epoxy layer llll. H6. 2 shows thevibration-transferring epoxy layer 1111 including avibrationtransferring portion 19 which directly adheres to the bottomsurface of the transducers l0 and the bottom wall of the receptacle 2,and an anchoring portion 18 which surrounds the vibration-transferringportion and a part of the transducers 10 thereby securing thetransducers to the receptacle 2. Although FlGS. l and 2 show thevibratory apparatus l with the opening 6 of the receptacle 2 facing downin actual use the opening would be facing upward.

The receptacle 2 is made of a chemical and etchant-resistant materialfrom the group consisting of polyvinyl chloride, polypropylene,polytetrafluoro ethylene and polyethylene. Preferably, polyvinylchloride is used because of its ability to resist strong etchants and itis easily formed into any desired shape. lf the liquid held in thereceptacle is not an etchant (i.e., will not attach metal), thereceptacle may, in addition, be made of a suitable metal such asstainless steel, aluminum, nickel and the like. Typical liquids of thistype would include deionized water, acetone and methanol alcohol. It is,of course, recognized that the shape of the receptacle 2 may be modifiedto include cylindrical shapes of the receptacle 2 may be modified toinclude cylindrical shapes, circular shapes and the like as long as theyprovide a surface to which the transducer 10 can be attached. Althoughthe transducers are shown mounted to the bottom wall of the receptacle 2in FIGS. 1 and 2, they may be, if desired, attached to one of the sideretaining walls 3 without deviating from the essence of our invention.The purpose of the bead 7 is to facilitate the attachment of thetransducers 10 to the receptacle 2 by defining with the bottom wall ofthe receptacle 2 a cavity. The bead 7 may be formed during or after thefabrication of the original receptacle. An alternate embodiment of thisfunction would be to use a suitable removable mold. Another variablethat must be considered in determining the design of the receptacle 2 isthe thickness of the retaining wall 3 which is directly below thetransducers l and shown in FIG. 2 as A." This thickness is varieddepending on the material used for making the receptacle 2 and thefrequency of the transducer in order to maximize the efficiency ofapparatus 1 to produce a standing-wave system. For example, when thereceptacle 2 is made of polyvinyl chloride it has been found that Ashould be in the range of one-sixteenth-three-eighth inches fortransducer frequencies in the range of 25-40 kilocycles.

To assemble the structure shown in FIGS. 1 and 2 the receptacle 2 isplaced upside down on a workbench. In this way, the bead 7 and thebottom retaining wall of the receptacle define a cavity. The desirednumber of transducers 10 to be attached to the receptacle 2 are thenprovided. This attachment is accomplished using a vibration-transferringepoxy-adhesive layer 11 which consists of a vibration-transferringportion 19 and an anchoring portion 18. A coating ofvibration-transferring epoxy adhesive 19 is applied to the chemicallyclean bottom surface of the transducers l0. Concurrently, a sufficientamount of adhesive 19 is placed in the cavity to facilitate theattachment of the coated surface of the transducers 10 to the receptacle2. The epoxy adhesive 19 comprises a thixotroping filler and anondampening epoxy adhesive. The thixotroping filler is made of a fillerfrom the group including talc, calcium carbonate, and colloidal silica.The nondampening epoxy ad hesive is made of a resin from the groupconsisting of diglycidyl ether of bisphenol-A, cycle-aliphatic, andnovalac resins and a curing agent from the group consisting of aliphaticamine, aromatic amine, and acid anhydrides. Preferably, the epoxyadhesive 19 is made of a talc filler in combination with a diglycidylether of bisphenol-A resin and an aliphatic amine curing agent becausethis combination is curable at room temperature. Although layer 19 hassufficient adhesive strength to hold the transducers 10 to the bottomwall of the receptacle 2 by itself, it has an operational lifetime ofabout hours which in most applications is unacceptable. Therefore, toensure an operational lifetime of over 1,000 hours, an anchoring portion18 is used. In this embodiment, it is preferred that layer 19 should berestricted to the area directly below the cross-sectional area of thebase surface of the transducers as shown in FIG. 2. In addition, thevibration-transferring portion 19 has a higher modulus of rigidity thanthe anchoring portion 18. The anchoring layer 18 is then poured into thecavity so as to surround the vibration-transferring portion 19 and apart of the transducers 10. The amount of the anchoring portion 18 usedis determined by the requirements of the particular applications of theapparatus 1.

The anchoring portion 18 of the adhesive layer 11 is made of aheat-conductive filler and an epoxy adhesive. The heatconductive filleris made of a material from the group consisting of alumina, zirconiumorthosilicate and boron nitride. The epoxy adhesive is made of a resinfrom the group consisting of diglycidyl ether or bisphenol-A,cycle-aliphatic, and novalac resins which has been previously mixed witha diluent from the group including butyl glycidyl ether, phenyl glycidylether, allyl glycidyl ether and a cross-linking curing agent made fromthe group including polyamides and polyamines.

If it is desirable to contact additional heat away from thetransducer-retaining wall interface, a heat-transfer member 4 may beembedded in the adhesive layer 11 as shown in FIGS. 1 and 2. In apreferred embodiment 4 has a plurality of spaced 0 vention may becarried out in various ways and may take various forms and embodimentsother than the illustrative embodiments heretofore described.Accordingly, it is to be understood that the scope of the invention isnot limited by the details of the foregoing description, but will bedefined in the following claims.

What we claim as new and desire to secure by Letters Patent of theUnited States is:

l. A vibratory treatment apparatus comprising:

a chemical and etchant resistant receptacle for containing a body ofliquid and having a plurality of retaining walls;

at least one vibration-generating transducer;

a vibration-transferring epoxy-adhesive layer interposed between one ofsaid walls of said receptacle and said transducer thereby securing saidtransducer to said one of said walls;

and a heat-transfer member embedded in said vibrationtransferring epoxylayer.

2. A vibratory treatment apparatus as defined in claim 1 wherein saidheat-transfer member having a plurality of spaced openings therethroughto allow said epoxy-adhesive layer to flow through and fill in saidopenings.

3. A vibratory treatment apparatus comprising:

a chemicaland etchant-resistant receptacle for containing a body ofliquid and having a plurality of retaining walls; at least onevibration-generating transducer;

a vibration-transferring epoxy-adhesive layer interposed between one ofsaid walls of said receptacle and said transducer thereby securing saidtransducer to said one of said walls;

said epoxy layer having a vibration-transferring portion and ananchoring portion;

said vibration-transferring portion being made of a thixotroping fillerand a nondampening epoxy adhesive, and said anchoring portion being madeof a heat-conductive filler and an epoxy adhesive;

said vibration-transferring portion being directly adhered to the bottomsurface of said transducer and to one of said walls of said receptacle;

said anchoring portion surrounding both said vibrationtransferringportion and part of said transducer thereby securing said transducer tosaid one of said walls;

said vibration-transferring portion having a higher modulus of rigiditythan said anchoring portion.

4. A vibratory treatment apparatus as defined in claim 3 wherein saidfirst-mentioned epoxy adhesive is made of a resin from the groupconsisting of diglycidyl ether of bisphenol-A, cylco-aliphatic, andnovalac resins and a curing agent from the group consisting of aliphaticamine, aromatic amine, and acid anhydrides; said thixotroping filler ismade of a filler from the group including talc, calcium carbonate andcolloidal silica; said heat-conductive filler is made of a filler fromthe group consisting of alumina, silica, zirconium orthosilicate andboron nitride; said second-mentioned epoxy adhesive is made of a resinfrom the group consisting of diglycidyl ether of bisphenol-A,cyclo-aliphatic, and novalac resins which has been previously mixed witha diluent from the group including butyl glycidyl ether, phenyl glycedylether, allyl glycidyl ether and a cross-linking curing agent made fromthe group including polyamides and polyamines.

5. An ultrasonic vibratory treatment apparatus comprising:

a chemicaland etchant-resistant receptacle for containing a body ofliquid and having sidewalls and a bottom wall and a bead formed aroundthe outer edge of its bottom wall and defining with said bottom wall acavity;

at least one vibration-generating transducer;

a vibration-transferring epoxy-adhesive layer between said receptacleand said transducer said epoxy-adhesive layer having avibration-transferring portion and an anchoring portion, saidvibration-transferring portion being directly adhered to the bottomsurface of said transducer and to said bottom wall of said receptacle,said vibration-transferring portion having a higher modulus of rigiditythan said anchoring portion and said anchoring portion surrounding bothsaid vibration-transferring portion and part of said transducer therebysecuring said transducer to said bottom wall;

heat-transfer member having a plurality of spaced openings therethroughand embedded in said epoxy-adhesive layer;

said receptacle and said transducer and said epoxy-adhesive layer andsaid heat-transfer member all being adapted so that a standing-wavesystem is produced in a liquid having a lcnown cavitation threshold insaid receptacle responsive to a particular power input to saidtransducer.

6. An ultrasonic vibratory treatment apparatus as defined in claimwherein said receptacle is made of polyvinyl chloride, saidvibration-transfer portion is made of thixotroping filler and anondampening adhesive epoxy, and said anchoring portion is made of aheat-conductive filler and an epoxy adhesive.

7. An ultrasonic vibratory treatment apparatus as defined in claim 6wherein said first-mentioned epoxy adhesive is made of a resin from thegroup consisting of diglycidyl ether of bisphenol-A, cyclo-aliphatic,and novalac resins and a curing agent from the group consisting ofaliphatic amine, aromatic amine, and acid anhydrides; said thixotropingfiller is made of a filler from the group including talc, calciumcarbonate and colloidal silica; said heat-conductive filler is made of afiller from the group consisting of alumina, silica, zirconiumorthosilicate and boron nitride; and second-mentioned epoxy adhesive ismade of a resin from the group consisting of diglycidyl ether orbisphenol-A, cycl c-aliphatic, and novalac resins which has beenpreviously mixed with a diluent from the group including butyl glycidylether, phenyl glycidyl ether, allyl glycidyl ether and a cross-linkingcuring agent made from the group including polyamides and polyamines.

8. A vibratory treatment apparatus comprising:

a chemicaland etchant-resistant receptacle for containing a body ofliquid and having sidewalls and a nonmetallic, flexible bottom wall;

at least one vibration-generating transducer;

a vibration-transferring epoxy-adhesive layer interposed between thebottom wall of said receptacle and the entirety of said transducer andsecuring said transducer to said bottom wall;

and a body of anchoring adhesive material bonded to the receptacle andthe transducer and extended around said vibration-transferring layer;

said vibration-transferring epoxy layer having a higher modulus ofrigidity than said body of anchoring adhesive material.

1. A vibratory treatment apparatus comprising: a chemical and etchantresistant receptacle for containing a body of liquid and having aplurality of retaining walls; at least one vibration-generatingtransducer; a vibration-transferring epoXy-adhesive layer interposedbetween one of said walls of said receptacle and said transducer therebysecuring said transducer to said one of said walls; and a heat-transfermember embedded in said vibrationtransferring epoxy layer.
 2. Avibratory treatment apparatus as defined in claim 1 wherein saidheat-transfer member having a plurality of spaced openings therethroughto allow said epoxy-adhesive layer to flow through and fill in saidopenings.
 3. A vibratory treatment apparatus comprising: a chemical- andetchant-resistant receptacle for containing a body of liquid and havinga plurality of retaining walls; at least one vibration-generatingtransducer; a vibration-transferring epoxy-adhesive layer interposedbetween one of said walls of said receptacle and said transducer therebysecuring said transducer to said one of said walls; said epoxy layerhaving a vibration-transferring portion and an anchoring portion; saidvibration-transferring portion being made of a thixotroping filler and anondampening epoxy adhesive, and said anchoring portion being made of aheat-conductive filler and an epoxy adhesive; saidvibration-transferring portion being directly adhered to the bottomsurface of said transducer and to one of said walls of said receptacle;said anchoring portion surrounding both said vibration-transferringportion and part of said transducer thereby securing said transducer tosaid one of said walls; said vibration-transferring portion having ahigher modulus of rigidity than said anchoring portion.
 4. A vibratorytreatment apparatus as defined in claim 3 wherein said first-mentionedepoxy adhesive is made of a resin from the group consisting ofdiglycidyl ether of bisphenol-A, cylco-aliphatic, and novalac resins anda curing agent from the group consisting of aliphatic amine, aromaticamine, and acid anhydrides; said thixotroping filler is made of a fillerfrom the group including talc, calcium carbonate and colloidal silica;said heat-conductive filler is made of a filler from the groupconsisting of alumina, silica, zirconium orthosilicate and boronnitride; said second-mentioned epoxy adhesive is made of a resin fromthe group consisting of diglycidyl ether of bisphenol-A,cyclo-aliphatic, and novalac resins which has been previously mixed witha diluent from the group including butyl glycidyl ether, phenyl glycedylether, allyl glycidyl ether and a cross-linking curing agent made fromthe group including polyamides and polyamines.
 5. An ultrasonicvibratory treatment apparatus comprising: a chemical- andetchant-resistant receptacle for containing a body of liquid and havingsidewalls and a bottom wall and a bead formed around the outer edge ofits bottom wall and defining with said bottom wall a cavity; at leastone vibration-generating transducer; a vibration-transferringepoxy-adhesive layer between said receptacle and said transducer saidepoxy-adhesive layer having a vibration-transferring portion and ananchoring portion, said vibration-transferring portion being directlyadhered to the bottom surface of said transducer and to said bottom wallof said receptacle, said vibration-transferring portion having a highermodulus of rigidity than said anchoring portion and said anchoringportion surrounding both said vibration-transferring portion and part ofsaid transducer thereby securing said transducer to said bottom wall; aheat-transfer member having a plurality of spaced openings therethroughand embedded in said epoxy-adhesive layer; said receptacle and saidtransducer and said epoxy-adhesive layer and said heat-transfer memberall being adapted so that a standing-wave system is produced in a liquidhaving a known cavitation threshold in said receptacle responsive to aparticular power input to said transducer.
 6. An ultrasonic vibratorytreatment apparatus as defined in claim 5 wherein said receptacle ismade of polyvinyl chloride, said vibration-tRansfer portion is made ofthixotroping filler and a nondampening adhesive epoxy, and saidanchoring portion is made of a heat-conductive filler and an epoxyadhesive.
 7. An ultrasonic vibratory treatment apparatus as defined inclaim 6 wherein said first-mentioned epoxy adhesive is made of a resinfrom the group consisting of diglycidyl ether of bisphenol-A,cyclo-aliphatic, and novalac resins and a curing agent from the groupconsisting of aliphatic amine, aromatic amine, and acid anhydrides; saidthixotroping filler is made of a filler from the group including talc,calcium carbonate and colloidal silica; said heat-conductive filler ismade of a filler from the group consisting of alumina, silica, zirconiumorthosilicate and boron nitride; and second-mentioned epoxy adhesive ismade of a resin from the group consisting of diglycidyl ether orbisphenol-A, cyclo-aliphatic, and novalac resins which has beenpreviously mixed with a diluent from the group including butyl glycidylether, phenyl glycidyl ether, allyl glycidyl ether and a cross-linkingcuring agent made from the group including polyamides and polyamines. 8.A vibratory treatment apparatus comprising: a chemical- andetchant-resistant receptacle for containing a body of liquid and havingsidewalls and a nonmetallic, flexible bottom wall; at least onevibration-generating transducer; a vibration-transferring epoxy-adhesivelayer interposed between the bottom wall of said receptacle and theentirety of said transducer and securing said transducer to said bottomwall; and a body of anchoring adhesive material bonded to the receptacleand the transducer and extended around said vibration-transferringlayer; said vibration-transferring epoxy layer having a higher modulusof rigidity than said body of anchoring adhesive material.